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Analysis of casting defects with the Simcenter STAR-CCM+

Analysis of Casting Defects with Simcenter STAR-CCM+

The production of castings is always a challenge, and not everything always goes as planned. There are several factors that, when not managed, compromise the quality of one, or even a batch of parts that come out defective. A delivery defect is the deviation in quality or condition of an actual casting compared to an ideal product.


The Simcenter Star-CCM+ has models that accurately predict the most common defects that can compromise the quality of castings.


Common defects are:

  • Porosity

  • Oxides

  • Misruns

  • Gas Inclusion


Porosity


Micro porosity:


Criteria functions as empirical models to assess micro shrinkage

  • Niyama Criterion

  • Dimensionless Niyama Criterion

  • Require manual validation for different alloys against real casting



Macro porosity


For pure thermal simulations based on density based volume deficits in isolated liquid metal pockets


High fidelity macro shrinkage prediction for fully coupled simulations based on pressure drop in isolated liquid metal pockets allows to include buoyancy effects


Example of macroporosity with Star-CCM+

Oxides


Passive scalar based oxide prediction model:

  • Accumulates the time the metal phase is exposed to air

  • User can modify the underlying oxide accumulation law to include effects such as the amount of oixidizable amount of metal

  • The model does not influence the flow field but the effect of an oxide film on the flow may be included by oxide thickness based viscosities


Evaluating the filling front:

  • The filling front will usually transport the most of the oxides and dirt

  • By tracking the progress of the filling front and its final resting place, the oxide contamination can be estimated



Misruns


Concurrent solving of flow and solidification:

  • The solidification of metal and its effects on the filling of the mold is calculated concurrently to the actual flow


Mushy zone for technical alloys:

  • Modeling effects of growth and accumulation of metallic dendrites on the flow

  • Porous media approach

  • Influence of solidification on flow behavior


Flow stop model:

  • All fluxes across flow stopped cells are zeroed expect energy

  • For large pressure gradients or body forces (i.e. HPDC)


Example of misruns with Star-CCM+

Volume of Fluid multiphase model:


  • Inherently provides the spatial distribution between gas and metal phase

  • Post processing filling and phase distribution allows to assess gas inclusions

  • Transport equations are solved for the entire fluid domain, thus the gas phase is transported through the domain and interacts with the metal phase

    • Surface tension effects

    • Gas entrainment

    • Counter pressure due to venting and gas compression effects


Example of gas trapping with Star-CCM+

 

The production of castings presents complex challenges that can compromise the quality of your products. At CAEXPERTS, we use Simcenter Star-CCM+ to predict and resolve critical defects such as porosity, oxides and runtime errors. Schedule a meeting with us and discover how our advanced solutions can transform your casting processes, ensuring efficiency and superior quality. Contact CAEXPERTS today and raise the standard of your production!



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